Miniature light bulb

ABSTRACT

A miniature light bulb has a hollow cylindrical base into which the envelope of the bulb is inserted and from which a flat plug extends downwardly. The connecting wires of the bulb filament extend through the base to the plug to which they are mechanically and conductively secured.

limited States atet [72] Inventor Paul Albrecht Bamherg, Germany [21]Appl. No. 810,762 [22] Filed Mar. 26,1969 [45] Patented Nov. 9, 1971 73]Assignee W. Albrecht-KG. Bamberg Bamberg, Germany [32] Priority Apr. 6,1968 [33] Germany [31 A 29602 [54] MINIATURE LIGHT BULB 10 Claims, 7Drawing Figs.

[52[ U.S.Cl 313/318, 339/144 R, 339/145 R [51 Int. Cl 1101,]5/48, H0 1 j5/50 [50] FieldofSearch 313/318; 339/144, 145, 144 R, 145 R [56]References Cited UNITED STATES PATENTS 894,193 7/1908 Dean 339/144Primary Examiner-David Schonberg Assistant Examiner-Toby H. KusmerAttorney-Hane & Baxley ABSTRACT: A miniature light bulb has a hollowcylindrical base into which the envelope of the bulb is inserted andfrom which a flat plug extends downwardly. The connecting wires of thebulb filament extend through the base to the plug to which they aremechanically and conductively secured.

MINIATURE LIGHT BULB The invention relates to a miniature light bulbsuch as a light bulb with incandescent filament and more particularly toa light bulb with a flat base insertable into a correspondingly shapedbulb socket.

BACKGROUND Miniature light bulbs of the general kind above referred toare widely used as signal and indicating lights and more generally forillumination purposes, where the available space is limited, forinstance, in radio and television sets, automobiles, boats, toys, etc.

Light bulbs with a flat base as now known are made of glass and theconnecting wires for the filament of the bulb protrude from the baseagainst which they are flattened without being secured thereto. It hasbeen found that light bulbs with such loose connecting wires often donot make satisfactory contact when fitted into the bulb socket. Theconnecting wires tend to become laterally displaced so that one or bothof the wires do not engage the terminal points of the socket. It is alsotechnically difficult or even practically impossible to mass produce aflat base made of glass with tolerances close enough to assure anadequate pressure fit in the socket. Moreover, a flat glass base beingrather delicate can be easily mechanically damaged so that the bulb mustbe discarded.

It is a broad object of the invention to provide a novel and improvedminiature light bulb of the general kind above referred to which assuresgood contact connections, is safely held in its socket and not easilymechanically damaged.

A more specific object of the invention is to provide a novel andimproved miniature light bulb of the general kind above referred towhich can be economically produced by typical mass productiontechniques.

SUMMARY OF THE INVENTION The afore pointed out objects, features andadvantages and other objects, features and advantages which will bepointed out hereinafter are obtained by providing a hollow cylindricalbase made of a suitable plastic material. The upper part of the basereceives the envelope of the bulb and the lower part mounts a flat plug.The connecting wires for the filament of the bulb are extended throughthe base mechanically and conductively secured on the end wall of theplug. A base made of plastic material can be produced in one operationand by typical mass production techniques with close tolerances so thatthe bulb is safely held in its socket thus assuring high qualitycontact. Moreover, the plastic base protects the bulb envelope, which isusually made of glass, so that the same is protected against breakage.

To maintain the wire ends in position and separated from each other, theinvention provides that the plug of the bulb is divided by a partitionwall into two mutually parallel and substantially equal branches. Thispartition wall also serves as a further guide of the light bulb and inparticular of its plug in the socket into which the bulb is to beinserted.

According to a further aspect of the invention, the connecting wiresextend beyond the lower end of the plug so that the bulb can beconnected to a circuit, for instance, by soldering or welding withoutrequiring the use of a socket.

In order to make the miniature bulb also useful for connection toprinted circuit boards, the invention provides that the flat plug of thebulb includes bores or lengthwise grooves for accommodating theconnecting wires. A pole element is fitted into each groove or bore atthe bottom end of the plug and connected to the wires. Such poleelements can then be inserted into the conventional contact eyelets ofthe printed circuit board and soldered in position together with othercircuit components connected to the printed circuit board.

A particularly advantageous embodiment of the invention is to fit uponeach of the two branches of the plug a contact sleeve of generallyU-shaped cross section, the sleeves encompassing the branches on threesides and also the bottom ends thereof. It has been found that suchcontact sleeves assure a particularly high contact quality when the bulbis inserted into its socket. Moreover, the sleeves prevent displacementof the wires and protect the same against damage. -To facilitateinsertion of the bulb into its socket the contact sleeves may be taperedtoward the bottom ends thereof.

Retention of a bulb in its socket may be further improved by providingin the side walls of each contact sleeve a cutout which is engageablewith a spring in the socket. The edges in the contact elements definingthe cutouts may be readily made with sharp comers so that the springsare safely retained in the cutouts. In contradistinction thereto it istechnically very difficult to form sharp comer edges at recesses in aglass base. The comers in such base are usually rounded and hence arenot capable of locating springs as well as sharp comers.

The invention further provides that the connecting wires are secured onthe bottom side of the contact sleeves, for instance, by soldering orwelding. This has the advantage that the soldering or welding points donot come in frictional sliding engagement with the inner walls of thesocket when a bulb is inserted into the socket. Accordingly, theterminal points of the bulb are not likely to be damaged and are alsonot likely to accumulate dirt.

If the bulb is to be used for illumination purposes, its envelope ispreferably so arranged that it partly protrudes from the top of thehollow cylindrical base. I

If it is desired to maintain the overall dimensions of the lamp as smallas possible, the invention provides that the envelope is inserted withinthe base so that it does not protrude therefrom. Accordingly, light willemanate from the bulb in the form of a beam and in the direction of thelengthwise axis of the bulb.

Signal or indicating lamps are often required to produce a colored lightsuch as a red or green light to indicate specific circuit conditions.This can be easily accomplished by covering the top end of the base witha colored translucent cover. This cover is preferably detachably mountedso that differently tinted covers can be readily used.

Other objects, features and advantages will be pointed out hereinafterand set forth in the appended claims constituting part of theapplication.

In the accompanying drawing several preferred embodiments of theinvention are shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is an elevational side view of a miniature light bulb accordingto the invention,

FIG. 2 is an elevational view of the bulb taken in the direction ofarrow ll of FIG. 1,

FIG. 3 is a section taken on line IIIIII of FIG. 2,

FIG. 4 is an elevational view similar to FIG. 1 of a modification of thelight bulb,

FIG. 5 is an elevational view similar to FIG. I of another modificationof the light bulb,

FIG. 6 is an elevational view similar to FIG. 1 of still anothermodification of the light bulb; and

FIG. 7 is a section similar to the section of FIG. 3 but showing amodification of the bulb base.

Referring now to the figures more in detail, the light bulb comprises asealed and evacuated envelope 1 in which a filament 17 such as anincandescent filament is mounted in a conventional fashion. The envelopeis fitted in an upper portion 2 of a hollow cylindrical base 3 made of asuitable plastic material such as polyvinylchloride. According to FIGS.I to S the envelope protrudes from the base and according to FIG. 6 theenvelope 1 is fully concealed within its base.

Base 3 has at its lower end a flat or pinched plug 4 the end 5 of whichis preferably tapered to facilitate the insertion of the bulb into asocket (not shown). A partition wall 6 divides the base into twopreferably substantially equal branches 8. The partition wall ispreferably also tapered at its end 7 and protrudes sidewise and endwisefrom the plug. Each branch 8 includes lengthwise bores 9 as is shown inFIG. 3 or grooves 16 in one of its sidewalls as shown in FIG. 7.

1. A miniature light bulb with pinched plug insertable into a bulbsocket, said bulb comprising: a closed envelope including a filament; abase made of synthetic plastic material and having a hollow cylindricalupper portion and a lower portion, said upper portion encompassing saidenvelope portion and said lower portion constituting a plug having asubstantially rectangular cross section; a pair of lead-in wiresconnected at one end to the filament, the other ends of the wiresprotruding from the envelope, and terminal strips having a channeledcross section, the web of each of said strips abutting against oppositesides of the plug and the branches of the strips straddling the sides ofthe plug adjacent to said opposite sides, said lead-in wires beingmechanically and conductively secured to said terminal strips.
 2. Thebulb according to claim 1 wherein said webs of the terminal strips restagainst the short sides of the plug and are extended and bent off tooverlie parts of the end wall of the plug also.
 3. The bulb according toclaim 1 whErein said lead-in wires extend along the length of the plugand are secured to inside surfaces of the terminal strips.
 4. The bulbaccording to claim 1 wherein a lengthwise rib protrudes from each ofsaid adjacent sides of the bulb and is interposed between the facingedges of the branches of the terminal strips.
 5. The bulb according toclaim 1 wherein part of said envelope protrudes above the cylindricalportion of said base.
 6. The bulb according to claim 1 wherein saidenvelope is fully concealed within the cylindrical portion of said base.7. The bulb according to claim 6 wherein a translucent cover closes theupper end of said cylindrical portion of the base.
 8. The bulb accordingto claim 1 wherein said plug includes lengthwise openings, and whereinpole elements are secured to the end wall of the plug, said lead-inwires extending through said openings and being connected to said poleelements.
 9. The bulb according to claim 1 wherein said plug haslengthwise grooves in two of its sidewalls, and wherein pole elementsare secured to the end wall of the plug, said lead-in wires beingdisposed within said grooves and connected to said pole elements. 10.The bulb according to claim 1 wherein said plug and the terminal stripsthereon are tapered toward the lower end thereof.